|Bridge name|Location|Year completed|Total length|Carries|
|---|---|---|---|---|
|Old Youngs Bay Bridge|Astoria, Oregon|1921|1,766.2 feet (538.3 m)|U.S. Route 101|
|Oregon City Bridge|Oregon City, Oregon|1922|745 feet (227 m)|Oregon Route 43|
|Dry Canyon Creek Bridge|near Rowena, Oregon|1922|101.1 ft|U.S. Route 30|
|Winchester Bridge|Winchester, Oregon|1923|884 feet|Oregon Route 99|
|Lewis and Clark River Bridge|Astoria, Oregon|1924|828 feet|U.S. Route 101|
|Ellsworth Street Bridge|Albany, Oregon|1925|1,090 feet|U.S. Route 20|
|Rocky Creek Bridge|Lincoln County, Oregon|1927|360 feet|U.S. Route 101|
|Depoe Bay Bridge|Depoe Bay, Oregon|1927|312 feet|U.S. Route 101|
|Crooked River High Bridge|Jefferson County, Oregon|1926|464 feet|U.S. Route 97|
|Big Creek Bridge|Lane County, Oregon|1931|180 feet|U.S. Route 101|
|Ten Mile Creek Bridge|near Yachats, Oregon|1931|180 feet|U.S. Route 101|
|Wilson River Bridge|Tillamook County, Oregon|1931|180 feet|U.S. Route 101|
|Rogue River Bridge|Grants Pass, Oregon|1931|550 feet|Redwood Highway|
|Cape Creek Bridge|near Heceta Head|1932|619 feet (188.6 m)|U.S. Route 101|
|Isaac Lee Patterson Bridge|Gold Beach, Oregon|1932|1,898 feet (578.5 m)|U.S. Route 101|
|John McLoughlin Bridge|Oregon City, Oregon|1933|720 feet|Oregon Route 99E|
|Umpqua River Bridge|Reedsport, Oregon|1936|2,206 feet|U.S. Route 101|
|Siuslaw River Bridge|Florence, Oregon|1936|1,568 feet|U.S. Route 101|
|Alsea Bay Bridge|Waldport, Oregon|1936|3,028 feet|U.S. Route 101|
|Yaquina Bay Bridge|Newport, Oregon|1936|3,223 feet (982 m)|U.S. Route 101|
|Coos Bay Bridge|North Bend, Oregon|1936|5,305 feet (1.6 km)|U.S. Route 101|

Question: how many bridges were built in 1931?
Answer: 4